package com.kuang.response;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

@WebServlet("/imgServlet")
public class ImgServlet extends HttpServlet {


    /**
     * 此处是生成验证码
     * @param req
     * @param resp
     * @throws ServletException
     * @throws IOException
     */
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //如何让浏览器5秒自动刷新一次
        resp.setHeader("refresh", "5");

        //在内存中创建一个图片
        BufferedImage image = new BufferedImage(80, 20, BufferedImage.TYPE_INT_RGB);

        //得到图片
        //笔
        Graphics2D graphics = (Graphics2D) image.getGraphics();

        //设置图片的背景颜色
        graphics.setColor(Color.WHITE);
        graphics.fillRect(0, 0, 80, 20);

        //给图片写数据
        graphics.setColor(Color.BLUE);
        //设置字体
        graphics.setFont(new Font(null, Font.BOLD, 20));
        graphics.drawString(makeNum(), 0, 20);

        //告诉浏览器，这个请求用图片的方式打开
        resp.setContentType("image/jpeg");
        //网站存在缓存，不让浏览器缓存
        resp.setDateHeader("expires", -1);
        resp.setHeader("Cache-Control", "no-cache");
        resp.setHeader("Pragma", "no-cache");

        //把图片写给浏览器
        ImageIO.write(image, "jpg", resp.getOutputStream());


    }

    //生成随机数
    private String makeNum() {
        Random random = new Random();
        String num = random.nextInt(99999999) + "";

        StringBuffer sb = new StringBuffer();

        for (int i = 0; i < 7 - num.length(); i++) {
            sb.append("0");
        }
        num = sb.toString() + num;
        return num;
    }


    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}
